System and method of facilitating connection between cannulae and a blood pump

ABSTRACT

A system for facilitating fluid connection between cannulae and a blood pump. The system includes a cannula having proximal and distal ends. The distal end of the cannula adapted to be in fluid communication with the circulatory system. The proximal end of the cannula configured to couple to an inlet of the blood pump. The system further includes a tunneling device configured to be inserted into a body of a patient to direct the proximal end of the cannula adjacent to the inlet for connection thereto. The cannula further includes a first connecting structure. The tunneling device further includes a second connecting structure. The first and second connecting structures are selectively engageable to allow connection and disconnection between the cannula and tunneling device.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Application Ser. No. 61/839,580filed Jun. 26, 2013 (pending), the disclosure of which is herebyincorporated by reference herein.

TECHNICAL FIELD

The invention generally relates to blood pumps and ancillary devices forconnecting the blood pump to associated cannulae.

BACKGROUND

The human heart is the muscle that is responsible for pumping bloodthroughout the vascular network. Veins are vessels that carry bloodtoward the heart while arteries carry blood away from the heart. Thehuman heart consists of two atrial chambers and two ventricularchambers. Atrial chambers receive blood from the body and theventricular chambers, which include larger muscular walls, pump bloodfrom the heart. A septum separates the left and the right sides of theheart. Movement of the blood is as follows: blood enters the rightatrium from either the superior or inferior vena cava and moves into theright ventricle. From the right ventricle, blood is pumped to the lungsvia pulmonary arteries to become oxygenated. Once the blood has beenoxygenated, the blood returns to the heart by entering the left atrium,via the pulmonary veins, and into the left ventricle. Finally, the bloodis pumped from the left ventricle into the aorta and the vascularnetwork.

For the vast majority of the population, the events associated with themovement of blood happen without circumstance. However, for many peoplethe heart fails to provide adequate pumping capabilities. These heartfailures may include congestive heart failure (commonly referred to asheart disease), which is a condition that results in any structural orfunctional cardiac disorder that impairs the ability of the heart tofill with or pump blood throughout the body. Presently, there is noknown cure for heart disease and long-term treatment is limited to aheart transplant. With only a little over 2,000 patients receiving aheart transplant each year, and over 16,600 more on the waiting list fora heart, there is a persisting need for a cure or at the minimum a meansof improving the quality of life of those patients on the waiting list.

One such means of bridging the time gap while awaiting a transplant is acirculatory assist system. Circulatory assist systems may also beutilized as a destination therapy for individuals not eligible for aheart transplant. These systems, originally envisioned over thirty yearsago, provide assistance to the heart by way of a mechanical pump. Inthis way, blood is circulated throughout the vascular network despitethe diseased heart tissue. Traditionally, these circulatory assistsystems include an implantable or extracorporeal pump, a controller(internal or external), and inflow and outflow tubes connecting the pumpto the heart and the vascular network. Food and Drug Administration(FDA) approved circulatory assist systems can partially relieve symptomsof breathlessness and fatigue associated with severe heart failure anddrastically improve quality of life.

Implantable pumps may reside in a “pump pocket,” which is a subcutaneousor submuscular space on the chest of a patient, near the clavicle orshoulder. Once the inflow tube is connected to the heart, it normallyresides within the thoracic cavity until connected with the pump. Inorder to access the chest cavity and reach the tube, practitioners musttunnel through the intercostal space adjacent the pump pocket. Once inthe thoracic cavity, the practitioner is able to grasp the inflowcannula and direct it to the pump pocket for connection to the pump.Currently, when tunneling through the intercostal space, surgeons resortto general surgical tools at their disposal, such as an anastomoticclamp or forceps. However, such tools may tear or otherwise injure theintercostal tissue when being forced into the intercostal space.Moreover, due to the high amount of force required to tunnel through theintercostal muscle, there is a risk of harming the patient, such asrupturing a vessel. Therefore, there is a need in the art for a systemand method which allows for a more controlled procedure of connecting ablood pump with the necessary tubing.

SUMMARY

It is therefore desirable to provide a system and method that allows forconnection of a cannula and a blood pump in a controlled manner.Furthermore, rather than relegating the practitioner to grasping theproximal end of the cannula as described above, it is desirable toprovide the cannula and other system components with features on, as apart of, or insertable into the cannula and other components, that allowfor a connection between the cannula and the blood pump. To that end, asystem for facilitating fluid connection between a blood pump and acirculatory system of a patient is provided. The system includes acannula having proximal and distal ends. The distal end of the cannulaadapted to be in fluid communication with the circulatory system. Theproximal end of the cannula is configured to couple to an inlet of theblood pump. The system further includes a tunneling device configured tobe inserted into a body of a patient to direct the proximal end of thecannula adjacent to the inlet for connection thereto. The cannulafurther includes a first connecting structure. The tunneling devicefurther includes a second connecting structure. The first and secondconnecting structures are selectively engageable to allow in situconnection and disconnection between the cannula and tunneling device.In some embodiments, the first and second connecting structures areconfigured to frictionally secure one another in order to provide theselective engagement. For example, the frictional securement may beprovided by features on one or both of the first or second connectingstructures that provide a snap fit therebetween. In other embodiments,however, one or more separate elements, such as a loop of suture orother material, may be used to provide the selective engagement betweenthe first and second connecting structures.

Another embodiment of a system for facilitating fluid connection betweena blood pump and a circulatory system of a patient is provided. Thesystem includes a cannula having proximal and distal ends. The distalend of the cannula is adapted to be in fluid communication with thecirculatory system. The proximal end of the cannula is configured tocouple to an inlet of the blood pump. The system further includes a plugconfigured to be inserted into the proximal end of the cannula and atunneling device configured to be inserted into a body of a patient. Theplug further includes a first connecting structure. The tunneling devicefurther includes a second connecting structure. The first and secondconnecting structures are selectively engageable to allow in situconnection and disconnection between the cannula and tunneling device.

A method of facilitating fluid connection between a blood pump and acirculatory system of a patient is also provided. The method includesdirecting a distal end of a cannula into fluid communication with thecirculatory system. The method further includes inserting the blood pumpinto a body of the patient and inserting a tunneling device into thebody of the patient. The method further includes selectively engaging afirst connecting structure of the cannula with a second connectingstructure of the tunneling device and directing a proximal end of thecannula adjacent to an inlet of the blood pump. The method furtherincludes connecting the proximal end of the cannula to the inlet.

BRIEF DESCRIPTION

FIG. 1A is a diagrammatic view of a circulatory assist system, includinga blood pump and multiple cannulae, in accordance with one embodiment ofthe invention, with the heart of a patient shown in partialcross-section.

FIGS. 1B through 1D are diagrammatic views of different steps associatedwith facilitating a connection between a cannula and the blood pump.

FIG. 2 is a perspective view of a tunneling device according to oneembodiment of the invention.

FIG. 3 is a perspective view of a tunneling device according to analternative embodiment of the invention.

FIG. 4 is a perspective view of the tunneling device of FIG. 3 showingrelative movement between components.

FIGS. 5A and 5B are perspective views showing different embodiments oflocking mechanisms of the embodiment of FIG. 3 to prevent relativemovement between components.

FIGS. 6 through 9 are detailed perspective views of various embodimentsof second connecting structures of tunneling devices, such as thoseshown in FIGS. 2 and 3.

FIGS. 10 through 12 are perspective views of various additionalembodiments of cannula plugs.

FIG. 13 is a perspective view showing one manner of engagement between atunneling device and a cannula plug.

FIGS. 14A and 14B show an alternative manner of engagement between atunneling device and a cannula plug.

FIGS. 15A and 15B show yet another alternative manner of engagementbetween a tunneling device and a cannula plug.

FIGS. 16A-16D show yet another alternative manner of engagement betweena tunneling device and a cannula plug.

FIGS. 17A-17D show yet another alternative manner of engagement betweena tunneling device and a cannula plug.

DETAILED DESCRIPTION

With respect to FIG. 1A, for illustrative purposes, certain anatomy isshown including the heart 12 of the patient 14 having a right atrium 16,a left atrium 18, a right ventricle 20, and a left ventricle 22. Bloodfrom the right and left subclavian veins 24, 26 and the right and leftjugular veins 28, 30 enters the right atrium 16 through the superiorvena cava 32 while blood from the lower parts of the body enters theright atrium 16 through the inferior vena cava 34. The blood is pumpedfrom the right atrium 16, to the right ventricle 20, and to the lungs(not shown) to be oxygenated. Blood returning from the lungs enters theleft atrium 18 via pulmonary veins 36 and is pumped into the leftventricle 22. Blood leaving the left ventricle 22 enters the aorta 38and flows into the left subclavian artery 40, the left common carotid42, and the brachiocephalic trunk 44, including the right subclavianartery 46 and the right common carotid 48.

Two cannulae 50, 52 (inflow and outflow, respectively) extend betweencardiovascular structures and a pump 54, which may be any implantable orextracorporeal pump 54 that is radially- and/or axially-driven. Thoseskilled in this art, however, recognize that other types of pumps may beused in other embodiments but may include pumps such as those describedin U.S. Pat. No. 8,157,720, which is incorporated herein by reference inits entirety, or commercially-available pumps, such as the SYNERGYPocket Micro-Pump from CircuLite, Inc. (Saddle Brook, N.J.), which iscapable of delivering blood flow at rates ranging from about 3 L/min toabout 4 L/min.

The inflow cannula 50 may be any suitable intravascular cannula deviceconstructed from materials, such as an extruded aliphatic,polycarbonate-base polyurethane; aliphatic polyether polyurethane;aromatic polyether polyurethane; aromatic polycarbonate basedpolyurethane; silicone modified polyurethane; or silicone. Antimicrobialagents may be embedded within the inflow cannula 50 material prior tothe forming process to effectively reduce or eliminate the presence of abio-film and reduce the potential for infection. Alternatively, theantimicrobial agent may be applied to the surface of the inflow cannula50 after the molding process is complete.

A reinforcing structure (not shown) may be included in the inflowcannula 50 construction to reduce the likelihood of kink formation. Thereinforcing structure may be, for example, a braided or coiledconstruction of a metal wire, such as stainless steel or Nitinol(nickel-titanium), or a polymeric material, such as KEVLAR (E.I. du Pontde Nemours and Co., Wilmington, Del.). The construction material mayhave various cross-sectional shapes, including, but not limited to,round and rectangular. If a round wire is used, the wire diameter maytypically vary from about 0.001 inch (0.0254 mm) to about 0.005 inch(0.127 mm). If the material has a rectangular cross-section, therectangle may typically have a height ranging from about 0.001 inch(0.0254 mm) to about 0.005 inch (0.127 mm) and a width ranging fromabout 0.003 inch (0.0762 mm) to about 0.010 inch (0.254 mm).

The inflow cannula 50 includes proximal and distal ends 56, 58. Thedistal end 58 of the inflow cannula 50 may include a tip 60, which isdescribed in greater detail in U.S. patent application Ser. No.13/025,757, which is incorporated herein by reference in its entirety.The illustrative tip 60 includes one or more openings 60 that extendproximally from a distal tip. The openings 60 permit the flow of bloodfrom the left ventricle 22 into a lumen 75 of the inflow cannula 50 evenin the event that the distal tip end becomes obstructed with tissue fromwithin the left ventricle 22. The tip 60 may be constructed from apolished titanium or other suitable material and have a design thatreduces fluidic turbulence and the risk of thrombosis formation. The tipdesign may also facilitate the coupling of the tip 60 to the distal end58 of the inflow cannula 50. For example, in some embodiments, aproximal end of the tip 60 may include one or more barbs (not shown) toprovide resistance against undesired removal of the tip 60 from theinflow cannula 50.

The outflow cannula 52 extends from an outflow port or outlet 62 of thepump 54 to an arterial access site 64, which is illustrated herein aswithin the aorta 38. The outflow cannula 52 may include a constructionthat is generally similar to the inflow cannula 50; however, a distalend 66 of the outflow cannula 52 is configured to be secured to thearterial access site 64. Accordingly, the distal end 66 may be securedby one or more sutures and/or include one or more anastomotic connectors(not shown), such as those taught in U.S. patent application Ser. No.12/829,425, the disclosure of which is incorporated herein by reference,in its entirety. The outflow cannula 52 may be tapered distally, similarto the inflow cannula 50, so that a proximal end 68 has a largerdiameter that accommodates the outflow port 62 of the pump 54 and asmaller diameter cannula body 70 accommodates the anatomy of the patient14. Again, for exemplary purposes only, the proximal end 80 may have adiameter that ranges from about 8 mm to about 11 mm while the diameterof the cannula body 82 may range from about 3 mm to about 7 mm.

As shown in FIG. 1B, the practitioner has inserted a tip 60 of an inflowcannula 50 into a cavity of the heart 12, and more specifically, theleft ventricle 22. Because much of the discussion hereinbelow focuses oninflow cannula 50, “inflow cannula” and “cannula” are usedinterchangeably herein and are meant to refer to reference numeral 50.In order to prevent blood from traveling through and out of the cannula50, the proximal end of the cannula 50 includes a cannula plug 72.“Cannula plug” and “plug” are used interchangeably herein and are meantto refer to reference numeral 72. As shown, the physician has directedthe remainder of the cannula 50 into through the thoracotomy incision 74such that the cannula 50 is resting within the thoracic cavity 76. Thethoracotomy as described herein may be a mini-thoracotomy, as understoodby those skilled in the art, made at the fourth intercostal space 80.However, the thoracotomy as disclosed herein need not occur at thefourth intercostal space 80 and may occur elsewhere according to thecharacteristics of the patient as well as the preferences of thepractitioner.

At this point, the practitioner also has inserted the pump 54 into thepump pocket 78, which may be subcutaneously or submuscularly situated.The steps involved in creating a pump pocket 78 will be apparent tothose skilled in the art. Alternatively, the physician may create thepump pocket 78 on the patient, but may wait to insert the pump 54 intothe pocket once connected to the cannula 50. The proximal end of thecannula 50 and the inlet or inflow port 82 of the pump 54 must then beconnected in order to close the loop of the circulatory assist system.

In order to connect the cannula 50 with the pump 54 in situ, thepractitioner may direct a tunneling device 84 through the pump pocket78, further into an intercostal space, and into the thoracic cavity 76.As described herein, connecting or connection “in situ” is meant todescribe connecting or connection inside the body, such as, for example,inside the thoracic cavity. The tunneling device 84 described herein isparticularly advantageous for accessing the thoracic cavity 76 throughan intercostal space. For this reason, the system and method isdescribed herein with a frame of reference to such anatomical areas. Theinvention, however, is not limited to the chosen frame of reference andsuch descriptive terms, and may be utilized for accessing parts of apatient's body other than those shown. For example, the system 10 may beutilized wherever it is advantageous to use a tunneling device 72,including on the opposite side of the chest to that shown in FIGS.1A-1E. More specifically, the system 10 may be utilized on the rightside of the chest to support different methods and devices, such asthose taught in U.S. patent application Ser. No. 12/144,738, thedisclosure of which is incorporated herein by reference, in itsentirety.

In one embodiment, the tunneling device 84 is directed through thesecond intercostal space 86. Therefore, in that embodiment, the pumppocket 78 may be situated such that the second intercostal space 86 isaccessible, in order for the tunneling device 84 to be directed throughthe pump pocket 78, and into and through the second intercostal space86. However, in other embodiments, the tunneling device 84 may bedirected into a different intercostal space or at a different area ofthe body. Where the tunneling device 84 is directed into the bodyultimately depends on the configuration of the tunneling device 84 andancillary devices, as well as the position of the pump 54 and pumppocket 78. As described in more detail below, the tunneling device 84 isconfigured to be inserted into the body in a controlled manner bydilating, rather than tearing or otherwise injuring, the intercostaltissue. The tunneling device 84 is further configured to prevent damageto structures when being directed into the body. Once the tunnelingdevice 84 is directed through the intercostal space, the practitionermay direct the tunneling device 84 further through the thoracic cavity76 towards the proximal end 56 of the cannula 50. Then, once the distalend 88 of the tunneling device 84 is adjacent or near the proximal end56 of the cannula 50, the practitioner may provide a connection betweenthe tunneling device 84 and the cannula 50. As described in more detailbelow, the cannula 50 and the tunneling device 84 include connectingstructures 90, 92 which allow for selective engagement between thecannula 50 and the tunneling device 84, which allow connection anddisconnection between the cannula 50 and the tunneling device 84 withinthe body of the patient. Although the connecting structures allow forthis, it is important to note that a user may decide to actually makethe connection while at least a connecting portion of the cannula 50 isoutside the body. More specifically, the cannula 50 includes a firstconnecting structure 90 and the tunneling device 84 includes a secondconnecting structure 92. In some embodiments, where a cannula plug 72 isinserted into the proximal end of the cannula 50, the first connectingstructure 90, or a portion of the first connecting structure 90, may beincluded on, or as a part of, the cannula plug 72.

In order to connect the cannula 50 with the tunneling device 84, thepractitioner may be required to reach into the thoracic cavity 76 toengage the first and second connecting structure 90, 92. Alternatively,where the proximal end 56 of the cannula 50 is residing exterior to thebody, the practitioner may also direct the distal end 88 of thetunneling device 84 outside of the body, thereby allowing thepractitioner to connect the cannula 50 and the tunneling device 84.

After connecting the cannula 50 and the tunneling device 84, the surgeonmay retract the tunneling device 84 such that the cannula 50, connectedwith the tunneling device 84, is directed towards the pump pocket 78where the pump 54 resides. Alternatively, instead of retracting theentire tunneling device 84, the tunneling device 84 may be configuredsuch that a first elongate dilator 94 thereof may move relative to asecond elongate dilator 96 (FIGS. 3 through 5B). As will be described inmore detail below, the first elongate dilator 94, which may be connectedto the cannula 50, may be retracted through a lumen 97 in the secondelongate dilator 96, while the second elongate dilator 96 remains in itsposition dilating the intercostal space. In some embodiments, thecannula plug 72 is configured to dilate tissue. More specifically, asthe tunneling device 84 is retracted further proximally such that thecannula plug 72 is entering the intercostal space, the cannula plug 72will traverse the same path through the tissue. Once the cannula plug 72dilates and traverses through the intercostal space, the proximal end ofthe cannula 50 is also directed through such that it is adjacent theinlet 82 of the blood pump 54. At this point, the pump 54 may beresiding in the pump pocket 78 or may be residing out of the body. Inorder to communicate the proximal end of the cannula 50 with the inletof the pump 54, the practitioner may remove the cannula plug 72.

In order to prevent blood from flowing from the proximal end of thecannula 50 once the cannula plug 72 is removed, the practitioner mayclamp the cannula 50 at a point distal of the proximal end. Afterremoving the cannula plug 72, the practitioner may then connect theproximal end 56 of the cannula 50 with the inlet of the pump 54, therebyclosing the loop of the circulatory assist device. The practitioner maythen unclamp the cannula 50 once the proximal end 56 thereof isconnected with the inlet 82, as shown in FIG. 1A.

One embodiment of a tunneling device 84 is shown in FIG. 2. Thetunneling device 84 includes a proximal end 100, a distal end 88, and ashaft 102 therebetween. In the embodiment shown in FIG. 2, the tunnelingdevice 84 is a unitary member such that relative movement between thedifferent portions is not provided. At least part of the tunnelingdevice 84 is defined as a dilator including a first elongate dilator 94,and a second elongate dilator 96 situated proximal of the first elongatedilator 94. As shown in FIG. 2, the tunneling device 84 further includesa distal, tapered tip 104 having a rounded end 106. The tapered tip 104and rounded end 106 are provided in order to gently dilate, rather thantear or otherwise injure, the intercostal space when directed into thebody. In some embodiments, the first and second elongate dilators 94, 96have a constant diameter along their lengths. The first elongate dilator94 has a first diameter 112 and the second elongate dilator 96 has asecond diameter 114. The second diameter 114 is larger than the firstdiameter 112. In other embodiments, however, the first and secondelongate dilators 94, 96 may not have a constant diameter along theirlengths. For example, only one of the first or second elongate dilators94, 96 may have a constant diameter along their lengths. Alternatively,one or both of the first and second elongate dilators 94, 96 may betapered along their lengths such that the diameters of each increasealong their lengths. Moreover, the tunneling device 84 may be defined bymore or less than two elongate dilators. For example, the tunnelingdevice 84 may be tapered along the entire length such that the tunnelingdevice 84 is defined as simply one elongate dilator. On the other hand,the tunneling device 84 may be defined as more than two elongatedilators, having tapered sections between each, like the tapered section110 shown in FIG. 2.

When directed into the intercostal space, the first elongate dilator 94dilates the tissue to a first stage. As the tunneling device 84 isfurther directed into the thoracic cavity 76 to a point where the secondelongate dilator 96 resides in the intercostal space, the tissue isdilated to a second stage. Depending on the anatomical characteristicsof the patient and dimensions of the tunneling device 84, during thesecond stage of dilation, the first elongate dilator 94 may residewithin the thoracic cavity 76, while a portion of the second elongatedilator 96 is enveloped by intercostal tissue. The distance into thebody that the tunneling device 84 must traverse in order to be connectedto the cannula 50 depends in part on the length of the tunneling device84, the location of the cannula 50, and the anatomy of the patient 14.

To provide for a more efficacious transition between the first andsecond stages of dilation, there is a tapered section 110 between thefirst and second elongate dilators 94, 96. The tapered section 110includes a generally frustoconical shape and is configured such thatthere is a constant increase in diameter between the first and secondelongate dilators 94, 96. However, the tapered section 110 need not beconfigured such that the diameter increases at a constant rate. Thetapered section 110 is provided to gradually dilate an opening in tissueas a practitioner inserts the tunneling device 84 further into the bodyof a patient 14, from the first stage of dilation to the second stage ofdilation. More specifically, the tapered section 110 is provided togradually dilate the tissue when the surgeon advances the tunnelingdevice 84 from a position where the tissue envelops the first elongatedilator 94 to a position where the tissue envelops the second elongatedilator 96.

In one embodiment, the first diameter 112 (of the first elongate dilator94) is between 3 and 6 mm, while the second diameter 114 (of the secondelongate dilator 96) is between 12 and 18 mm. The total length of thetunneling device 84 may be approximately 270-330 mm, but may be shorteror longer, depending on the desired characteristics of the tunnelingdevice 84, which may ultimately depend on the anatomy of the patient.The tapered tip 104 in one embodiment is included as a unitary part ofthe tunneling device 84 (FIG. 2) and as a unitary part with the firstelongate dilator 94 (FIGS. 3 & 4). In alternative embodiments, however,the tapered tip 104, and potentially the second connecting structure 92,may be disconnectable from the first elongate dilator 94. Providing sucha feature would allow a practitioner to interchange the dilating tip 104and/or the second connecting structure 92, depending on the desire ofthe practitioner, as well as the availability of or compatibility withcertain corresponding first connecting structures 90, as describedbelow.

The tunneling device 84 may be provided with enough stiffness in orderto pierce and traverse the intercostal tissue without buckling asubstantial amount, but with enough flexibility to flex, or be divertedaway, when contacting a relatively solid structure, such as bone.Moreover, the tapered tip 104 may be configured to push aside softtissue, such as vessels, in order to produce a minimal amount of trauma,or no trauma at all. The tunneling device 84 may possess a durometerbetween 40D and 75D. The tunneling device 84 may be one material of thesame material properties throughout. In other words, the entiretunneling device 84 may be of the same material having a singlestiffness, for example. On the other hand, the tunneling device 84 mayinclude different materials and/or characteristics along the length. Forexample, the tapered tip 104 may have different materials and/orcharacteristics than the first elongate dilator 94, which may havedifferent materials and/or characteristics than the second elongatedilator 96.

In some embodiments, the tunneling device 84 may comprise multiplelayers (not shown), each of which may impart certain characteristics tothe tunneling device 84. For example, the tunneling device 84 mayinclude inner and outer layers. More specifically, for example, theinner layer may include a material which may impart a desired stiffnessor flexibility, for example, to meet the desired characteristicsdescribed above when traversing the intercostal space. The outer layermay include a material to impart lubricity or another characteristicthat may assist in traversing the intercostal tissue. However, the outerlayer may also be provided to contribute to characteristics of thetunneling device 84, such as stiffness or flexibility.

In one embodiment, the tunneling device 84 may be reinforced (not shown)along at least a section thereof. The reinforced section may be providedalong the entire length of the tunneling device 84 or, alternatively,only along a certain portion. In a non-unitary embodiment, either one orboth of the first and second elongate dilators 94, 96 may include areinforced portion along at least a portion of their lengths. Thereinforced portion may include longitudinally disposed members, such asa polymeric, fabric or metallic monofilament, or a polymeric, fabric ormetallic polyfilament. Further, or alternatively, the reinforced sectionmay include coils embedded in the body of one or both of the first andsecond elongate dilators 94, 96. The coils may be helically wound alongthe length of the tunneling device 84. Alternatively, the coils may beseparate members, situated concentrically relative to a center axis ofthe tunneling device 84 and spaced apart along the length of thetunneling device 84. Preferably, the reinforced section or sections mayprovide stiffness during a pushing and pulling motion while stillproviding the desired flexibility. To facilitate easier insertion andremoval, the tunneling device 84 also may include a lubricious coatingon at least a portion of one or both of the first and second elongatedilators 94, 96, as well on as the tapered tip 104.

Proximal of the tapered tip 104, there may be a second connectingstructure 92. However, in some embodiments, a portion of the secondconnecting structure 92 may be on or within the tapered tip 104. Thesecond connecting structure 92 in the embodiments shown in FIGS. 2-4 and8 is defined at least in part by a hook 116. The hook 116 is furtherdefined by a generally L-shaped void 118 from the body of the firstelongate dilator 94. The hook 116 is configured to engage with a firstconnecting structure 90 (i.e., FIG. 13). The first connecting structure90 may be defined in part by a loop 120 (FIG. 13) of a suture or othermaterial that is coupled to, for example, an aperture 122 of the cannulaplug 72, which may be defined as the remaining part of the firstconnecting structure 90. However, the first connecting structure 90 mayalso be defined by only a portion of the cannula plug 72 (or voidtherein, such as the aperture 122 or cavity) that is selectivelyengageable with the second connecting element. The hook 116 may includea chamfer 124 to ease the connection with at least a portion of thefirst connecting structure 90, such as the loop 120 of suture or othermaterial. The hook 116 may be reinforced, for example, by providingsupplemental material thereon (not shown), or simply by providing moreamount of material at or near the hook 116.

At the proximal end 100 of the tunneling device 84, there may be a knobor handle 126 provided in order to assist the user in gripping thetunneling device 84 during use. In the embodiments shown, the knob orhandle 126 member is a cylindrical extension of the shaft 102 having athird diameter 128. As shown, the third diameter 128 is larger than thefirst and second diameters 112, 114. In alternative embodiments,however, the knob or handle 126 may be shaped or sized in a differentmanner than that shown in FIG. 2. The diameter of the knob as shown maybe between 15 and 21 mm. Further, the knob or handle 126 may include alarger diameter than that shown, or may be situated transverselyrelative to the tunneling device 84, rather than concentrically, asshown. Alternative handle or knob members may be included in order toprovide an ergonomic experience for the practitioner. Alternatively, inother embodiments, a handle 126 may not be provided.

As shown in FIGS. 3, 4, 5A & 5B, the tunneling device 84 may includemultiple components which are movable relative to one another. To thatend, the first and second elongate dilators 94, 96 are separate, nestedcomponents, such that the second elongate dilator 96 includes a lumen 97(shown in hidden lines) for receiving the first elongate dilator 94.Notably, the knob or handle 126 is provided at the proximal end 134 ofthe first elongate dilator 94.

Relative movement between the first and second elongate dilators 94, 96may be advantageous in certain situations. For example, when directingthe cannula 50 to the pump pocket 78 for connection to the pump inlet82, as described above, it may be advantageous to allow relativemovement between the first and second elongate dilators 94, 96. In thatsituation, the second elongate dilator 96 may remain within theintercostal space for dilation, as the first elongate dilator 94 isretracted through the lumen of the second elongate dilator 96 to directthe cannula 50 adjacent to the inlet. However, when the practitioner isdirecting the tunneling device 84 into (or out from) the intercostalspace, it may be advantageous to prevent the relative movement betweenthe first and second elongate dilators 94, 96. To that end, a lockingmechanism 130 for preventing relative movement between the first andsecond elongate dilators 94, 96 may be provided.

With reference to FIG. 5A, the locking mechanism 130 includes a firstthreaded section 132 adjacent the proximal end 100 of the first elongatedilator 94. The second elongate dilator 96 includes a second threadedsection 134, which is complementary to the first threaded section 132such that the first and second threaded sections 132, 134 may threadablyengage one another. In an alternative embodiment, as shown in FIG. 5B,the first elongate dilator 94 includes an L-shaped protrusion adjacentthe proximal end 134 of the first elongate dilator 94. The L-shapedprotrusion 138 is configured to be accepted into L-shaped slot 140 ofthe second elongate dilator 96. In order to prevent relative movementbetween the first and second elongate dilators 94, 96, the protrusion138 must be directed into the first portion 142 of L-shaped slot 140 androtated into and in engagement with the second, lateral portion 144. Thelocking mechanisms 130 as shown in FIGS. 5A and 5B, and as described inthis disclosure are meant to be illustrative. It is anticipated thatalternative designs of locking mechanisms 130 are possible.

The distal end 88 of a tunneling device 84, including differentembodiments of second connecting structures 92, are shown in FIGS. 6through 9. The tunneling device 84 shown in FIGS. 6 and 7 includes anelongate aperture 146 configured to engage with at least a portion of afirst connecting structure 90 connected to the cannula 50 or cannulaplug 72, such as a loop 120 of suture, umbilical tape, or othermaterial. The elongate shape of the aperture 146 is provided so that thepractitioner may provide an easy, quick connection, such as when tying aloop 120 of suture or other material thereto. The elongate shapeprovides further advantages, such as providing a space for at least partof the loop 120 to reside as the first elongate dilator 94 is retractedthrough the lumen 97 of the second elongate dilator 96, as describedabove. The elongate aperture 146 of FIG. 6 is shown to be moreproximally oriented than the elongate aperture 146 of FIG. 7. This maybe for providing additional space for the loop 120 to reside duringretraction. More specifically, the tunneling device 84 may optionallyinclude at least one elongate recess 148 adjacent the elongate aperture146. In some embodiments, two diametrically opposed elongate recesses148 are provided.

While the various embodiments of tunneling device 84 described hereinmay be directed into the body without the use of a guidewire, it may beadvantageous in some patients to utilize a guidewire to provide initialaccess to the body. The use of a guidewire to access the body will bewell understood by those skilled in the art. Therefore, an optionalguidewire lumen 150 may be provided. The optional guidewire lumen 150 isshown in the embodiments of FIGS. 6 and 7. However, it is anticipatedthat any of the embodiments of a tunneling device 84 as described hereinmay include a guidewire lumen 150.

With reference to FIGS. 10 through 12, each of the cannula plugs 72shown includes a proximal end 156, a distal end 158, and a body 160therebetween. At the proximal end 156 of the cannula plug 72 is astopper member 162. The stopper member 162 has a tapered, generallyfrustoconical shape that allows a practitioner to more easily insert thestopper member 162 into the lumen 75 of the cannula 50. In someembodiments, it may be provided that the stopper member 162 isconfigured to block flow of fluid from and seal the proximal end 56 ofthe cannula 50. The shape and configuration of the stopper member 162 asshown is but one embodiment, and it is appreciated that different shapesand configurations of the stopper member 162 that provide ease ofinsertion into the cannula 50 are possible. Preferably, the stoppermember 162 engages the lumen 75 of the cannula 50 with an amount ofinterference and frictional force sufficient to prevent the unwantedremoval of the cannula plug 72 from the cannula 50 during use. Asdiscussed in more detail below, the cannula plug 72 includes featuresthat may reduce the force required for traversing the cannula plug 72through the intercostal tissue. These features therefore may reduce thelikelihood of the unwanted removal of the cannula plug 72 from thecannula lumen 75. Extending distally from the stopper member 162 is agenerally cylindrical portion, or a neck 166, having a smaller outerdiameter than the stopper member 162. The configuration of the neck 166may provide an ease of removal benefit once the practitioner desires toremove the cannula plug 72 from the cannula 50.

Further distal along the body of the cannula plug 72, there is anelongate frustoconical member 168. In FIGS. 10 and 13, the elongatefrustoconical member 168 includes an aperture 122 near the distal end.As discussed herein, the aperture 122 may be provided as part of a firstconnecting structure 90 in order to selectively engage with a secondconnecting structure 92. The loop 120 may be considered as a part of oneof the first or second connection structures 90, 92, or as a part ofboth. As discussed above, once the first and second connectingstructures 90, 92 are engaged, the cannula 50 and the tunneling device84 are connected and the cannula 50 may be directed adjacent the inletof the pump 54 in the pump pocket 78.

FIG. 13 shows an embodiment where a separate element, such as the loop120, is provided for engagement between the first and second connectingstructures 90, 92. More specifically, loop 120 may be engaged with theaperture 122 and the hook 116, thereby connecting the cannula 50 and thetunneling device 84. In an alternative embodiment, the first connectingstructure 90 may be a hook, while the second connecting structure 92 maybe an aperture. Alternatively, both the first and second connectingstructures may be an aperture, similar or identical to aperture 122.Furthermore, as shown, the loop 120 includes a knot 121. In someembodiments, the loop 120 may be prepackaged as an assembly with thecannula plug 72 such that the loop 120 is tied and engaged with theaperture 122 before the operating setting, at the manufacturer.Alternatively, the practitioner may use a material such as suture, orany other material at his or her disposal, to tie the loop 120 in theoperating theatre.

At the distal end 158, the cannula plug 72 includes a rounded, taperedtip 170. As the tunneling device 84 is retracted to direct the cannula50 to the pump pocket 78, the cannula plug 72 must also traverse thetissue interior to the pump pocket 78, such as an adjacent intercostalspace. The tapered tip 170 and the elongate frustoconical member 168 areconfigured to gently dilate, rather than tear or otherwise injure, thetissue as the cannula plug 72 traverses the intercostal space. Notably,the location of the tissue into which the tunneling device 84 isdirected is the location where the cannula plug 72, and thus the cannula50, may exit. In at least one of the embodiments of the system asdescribed herein, the diameter of the largest portion of the elongatefrustoconical member 168 corresponds with, or is substantially equal to,the diameter of the second elongate dilator 96 of the tunneling device84. Providing the cannula plug 72 with a largest diameter substantiallyequal to that of the tunneling device 84 (not including the handle 126)may reduce the force required to direct the cannula plug 72 through theintercostal tissue, as the tissue will already have been dilated by thetunneling device 84. This benefit reduces the likelihood of the unwantedremoval of the cannula plug 72 from the proximal end of the cannula 50and also reduces trauma to the patient. The cannula plug 72 may also beprovided with a lubricious coating in order to reduce the frictionalforces associated with traversing the tissue.

FIGS. 8, 14A, and 14B show one embodiment of the system where the firstand second connecting structures 90, 92 are configured to frictionallyengage one another. More specifically, the first and second connectingstructures 90, 92 are configured to allow a snap fit therebetween. Tothat end, the distal end 172 of the elongate frustoconical member 168includes an aperture 174 communicating with a cavity 176. The aperture174, in combination with an opening 180, forms a penannular rib 178. Theopening 180 is defined by a void of material along a portion of thecircumference and the length of the elongate frustoconical member 168.The opening 180 is provided to impart resiliency characteristics uponthe elongate frustoconical member 168. More specifically, with referenceto FIGS. 14A and 14B, the distal end 88 of the tunneling device 84 isdirected through the aperture 174 and into the cavity 176. The largestdiameter (and potentially more proximally situated portions) of the tip104 of the tunneling device 84 in the embodiment shown is larger thanthe diameter of the aperture 174. Therefore, the opening 180 is providedto allow the elongate frustoconical member 168 to resiliently expand toa flexed position (not shown) until the groove 182 of the tunnelingdevice 84 mates with the rib 178 of the cannula plug 72, where theopening 180 of the elongate frustoconical member 168 is in a relaxedposition (FIG. 14B). The outer diameter of the first elongate dilator 94may be substantially equal to the largest outer diameter of the elongatefrustoconical member 168. These diameters may be substantially equal inorder to provide a smooth transition as the tunneling device 84 isretracted through the intercostal space to a point where the cannulaplug 72 traverses the intercostal space. In each of the embodimentsshown, the largest diameter of the elongate frustoconical member 168corresponds with, or is substantially equal to, the diameter of thesecond elongate dilator 96 such that the intercostal tissue continues tobe gently dilated as the cannula plug 72 traverses therethrough.

The resiliency and the shape of the opening 180 are also provided toallow for disconnection of the tunneling device 84 and cannula plug 72.More specifically, in order to disengage the tunneling device 84 andcannula plug 72, the practitioner may need to pull the distal end 88 ofthe tunneling device 84 towards the opening 80 such that the groove 182may disengage from the rib 178. The practitioner may continue to pullthe tunneling device 84 (and/or push the cannula plug 72) until theconnection between the tunneling device 84 and the cannula plug 72 nolonger exists.

FIGS. 9, 15A, and 15B show another embodiment of the system where thefirst and second connecting structures 90, 92 are configured tofrictionally engage one another. More specifically, the cavity 154 ofthe cannula plug 72 is configured receive and “grab,” or frictionallysecure the annular grooves 152 of the tunneling device 84. The annulargrooves 152 may be molded into the first elongate dilator 94 as anintegral component or, alternatively, may be a separately manufacturedand added component. The annular grooves 152 are configured to beaccepted into a cavity 154 of a cannula plug 72.

The cavity 154 may include an elastomeric material that is configured toallow the insertion of the tunneling device 84 therein. The materialalso is configured to prevent the removal of the tunneling device 84from the aperture when the tunneling device 84 is retracted to directthe cannula 50 to the pump pocket 78. Such materials may includesilicone or other elastomeric materials. The cannula plug 72 could beconfigured such that an inner portion including the cavity is anelastomeric material while the outer portion is a different material.Alternatively, the entire cannula plug 72 could comprise the elastomericmaterial. Notably, in the embodiment shown, at least the distal tip 104may be removable from the tunneling device 84 in order to facilitate theinteraction between the annular grooves 152 and the cavity 154.

FIGS. 16A-16D show one embodiment of the system where the first andsecond connecting structures 90, 92 are configured to threadably engage,or interlock, one another. More specifically, the second connectingstructure 92 may be defined in part by threads 184 and the firstconnecting structure 90 may be defined in part by threads 186 for matingwith the threads 184 of the second connecting structure 92. Furthermore,the tunneling device 84 may include a detachable tip 104 having threads188 for mating with the threads 184 of the second connecting structure92. In this manner, a practitioner may direct the tunneling device 84through a patient's intercostal space to a location proximate thecannula plug 72, as previously described and shown in FIG. 1B. Once thedistal end 88 of the tunneling device 84 is adjacent or near the firstconnecting structure 90, the practitioner may remove the detachable tip104 by disengaging the threads 188 of the detachable tip 104 from thethreads 184 of the second connecting structure 92, as shown in FIG. 16A.The practitioner may then provide a connection between the tunnelingdevice 84 and the cannula plug 72 by engaging the threads 186 of thefirst connecting structure 90 with the threads 184 of the secondconnecting structure 92, as illustrated in FIGS. 16B and 16C. This maybe facilitated by an elongate member such as a cable 190 coupled withthe second connecting structure 92 for providing selective rotation ofthe threads 184 of the second connecting structure 92. The cable 190 mayalso be coupled with the knob 126 (FIG. 16D) of the tunneling device 84such that the practitioner may cause the rotation of the threads 184 bymanually rotating the knob 126. The cable 190 may include annulargrooves 192 that may engage with corresponding annular rings 193 forretaining the cable 190 within the tunneling device 84. In order todisengage the tunneling device 84 and the cannula plug 72, thepractitioner may disengage the threads 184 from the threads 186. In theembodiment shown, threads 184 are external, or male, threads, whilethreads 186, 188 are internal, or female, threads. However, it should beappreciated that in other embodiments, threads 184 may be internal, orfemale, threads, and threads 186, 188 may be external, or male, threads.

In one embodiment, the first connecting structure 90 may include asleeve 194 that is defined in part by the threads 186 of the firstconnecting structure 90. The sleeve 194 may be independently rotatableof the cannula plug 72 to facilitate engagement of threads 186 withthreads 184 without disturbing the cannula plug 72 or the cannula 50(FIG. 16D). For example, the sleeve 194 may be positioned over andattached to a peg 196 that protrudes from the distal end 158 of thecannula plug 72, and the peg 196 may be affixed to an anchor 198 withinthe body 160 of the plug 72. In one embodiment, the distal end 158 maycomprise a substantially constant cross section. In one embodiment theanchor 198 may be retained in the cannula plug 72 directly during amolding process used to form the plug 72. The anchor may comprise alarger cross section than the peg 196 in order to provide a morepermanent hold. Furthermore, a screw 200 or other attachment means maybe placed into the peg 196 in order to retain the sleeve 194.Alternatively, in another embodiment the sleeve 194 may be attached tothe plug 72 by means of a rivet.

FIGS. 17A-17D show another embodiment of the system where the first andsecond connecting structures 90, 92 are configured to frictionallyengage one another. More specifically, the second connecting structure92 may be defined in part by a clip 202. For example, the clip 202 mayinclude a sleeve or collet 204 having a plurality of expandable flangesor arms 206. In one embodiment, the flanges or arms 206 may beconstructed of a metal material. Furthermore, the first connectingstructure 90 may be defined in part by a pin 208 for frictionallyengaging the clip 202. The pin 208 may protrude from the distal end 158of the cannula plug 72. Furthermore, the pin 208 may be affixed to ananchor 210 within the body 160 of the plug 72. Moreover, the tunnelingdevice 84 may include a detachable tip 104 having a pin 212 forfrictionally engaging the clip 202. In this manner, a practitioner maydirect the tunneling device 84 through a patient's intercostal space toa location proximate the cannula plug 72, as previously described. Oncethe distal end 88 of the tunneling device 84 is adjacent or near thefirst connecting structure 90, the practitioner may remove thedetachable tip 104 by disengaging the pin 212 of the detachable tip 104from the clip 202 of the second connecting structure 92, as shown inFIG. 17A. The practitioner may then provide a connection between thetunneling device 84 and the cannula plug 72 by engaging the pin 208 ofthe first connecting structure 90 with the clip 202 of the secondconnecting structure 92, as illustrated in FIGS. 17B and 17C. In oneembodiment, at least a portion of the clip 202 may be tapered in orderto provide a smooth transition as the tunneling device 84 is retractedthrough the intercostal space to a point where the cannula plug 72traverses the intercostal space. To this end, the clip 202 may be fixedto an elongate dilator 95, which may be connected to the first elongatedilator 94 of the tunneling device 84 with a tapered section 111provided therebetween.

In one embodiment, at least one of the pins 208, 212 may be tapered toprovide a smooth expansion of the flanges 206 as a pin 208, 212 isinserted into the clip 202. In addition, the pins 208, 212 may includerelief channels 214, 216. Furthermore, the clip 202 may include fingers218 positioned on the flanges 206, and the fingers 218 may be engageablewith the relief channels 214, 216 for securing a pin 208, 212 relativeto the clip 202, as shown in FIG. 17C. In order to disengage thetunneling device 84 and cannula plug 72, the practitioner may need topull the pin 208 away from the clip 202 such that the relief channel 214may disengage from the fingers 218. The second connecting structure 92may further include a retention sleeve 220 that may be slid over theclip 202 to secure the flanges 206 over a pin 208, 212, as illustratedin FIGS. 17C and 17D. For example, the retention sleeve 220 may movewith tension so that it may not slide back and forth freely. Rather, apractitioner may be required to manually retract the retention sleeve220 prior to disengaging the tunneling device 84 and cannula plug 72. Inaddition, the retention sleeve 220 may include a tapered section 222 inorder to provide a smooth transition as the tunneling device 84 isretracted through the intercostal space to a point where the cannulaplug 72 traverses the intercostal space.

While the figures may show the second connecting structures 92associated with a certain embodiment of the tunneling device 84, thedisclosure herein is not limited to such possibilities. It isanticipated that any of the second connecting structures 92 may beassociated with any embodiment of the tunneling device 84. Moreover,multiple second connecting structures 92 may be included on thetunneling device 84 in order to provide versatility in the procedure.For example, the tunneling device 84 may include a second connectingstructure 92, such as a hook 116, for accepting a loop 120, as well as athreaded portion (i.e., annular grooves 152) for engaging with thecavity of a cannula plug 72 as discussed above (FIGS. 12, 15 and 16). Itis possible in alternative embodiments that the cannula plug 72 mayinclude any of the second connecting structures 92 as described herein,while the tunneling device 84 may include any of the first connectingstructures 90 as described herein. Moreover, the first and secondconnecting structures 90, 92 may engage in manners other than thosedescribed herein. For example, one or both of the first and secondconnecting structures 90, 92 may include magnetic features that allowmagnetic coupling or engagement therebetween. More specifically, thefirst connecting structure 90 may comprise a first magnet (not shown),which may magnetically couple to a second magnet (not shown) thatcomprises the second connecting structure 92. Additionally, the cannulaplug 72 and/or the tunneling device 84 may include features tocomplement the magnetic engagement, or that provide additionalengagement force between the cannula plug and tunneling device,including features of the first and second connecting structures 90, 92described herein.

Furthermore, the force provided between the first and second connectingstructures 90, 92 must be configured to prevent the unwanteddisconnection of the cannula 50 from the tunneling device 84 as thetunneling device 84 and cannula 50 are retracted through the thoraciccavity 76, further through the intercostal space, and into the pumppocket 78. As discussed herein, the tunneling device 84 and the cannulaplug 72 may include features to reduce the forces that occur duringretraction through tissue.

While the present invention has been illustrated by a description ofvarious preferred embodiments and while these embodiments have beendescribed in some detail, it is not the intention of the Applicants torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. The various features of the invention may beused alone or in any combination depending on the needs and preferencesof the user. This has been a description of the present invention, alongwith the preferred methods of practicing the present invention ascurrently known. However, the invention itself should only be defined bythe appended claims.

What is claimed is:
 1. A system for facilitating fluid connectionbetween a blood pump and a circulatory system of a patient, comprising:a cannula having proximal and distal ends, the distal end of the cannulaadapted to be in fluid communication with the circulatory system, theproximal end of the cannula configured to couple to an inlet of theblood pump; and a tunneling device configured to be inserted into a bodyof a patient to direct the proximal end of the cannula adjacent to theinlet for connection thereto; wherein the cannula further comprises afirst connecting structure; and the tunneling device further comprises asecond connecting structure, the first and second connecting structuresbeing selectively engageable to allow in situ connection anddisconnection between the cannula and tunneling device.
 2. The system ofclaim 1, further comprising: a plug configured to be inserted in theproximal end of the cannula, the plug including at least a portion ofthe first connecting structure.
 3. The system of claim 1, wherein atleast one of the first or second connecting structures is defined atleast in part by an aperture for accepting a loop of material forconnection to the other of the first and second connecting structures.4. The system of claim 3, wherein the loop further comprises one of thefollowing: a suture, wire, or medical tape.
 5. The system of claim 1,wherein the first and second connecting structures are configured tofrictionally engage one another.
 6. The system of claim 5, wherein thefirst and second connecting structures are configured to allow a snapfit therebetween.
 7. The system of claim 2, wherein: the secondconnecting structure further comprises a groove on the tunneling device;and the first connecting structure further comprises: a cavity in theplug for receiving a distal portion of the tunneling device, and a ribon the plug, the rib engageable with the groove for securing thetunneling device relative to the plug.
 8. The system of claim 2, whereinthe plug further comprises proximal and distal ends and a bodytherebetween, at least a portion of the body being tapered for dilatingtissue.
 9. The system of claim 1, wherein at least one of the first orsecond connecting structures further comprises a hook.
 10. The system ofclaim 1, wherein the tunneling device further comprises: a firstelongate dilator; and a second elongate dilator proximal of the firstelongate dilator, wherein at least a portion of the second elongatedilator has a larger diameter than that of the first elongate dilator inorder to dilate tissue a greater amount than the first elongate dilator.11. The system of claim 10, wherein at least one of the first or secondelongate dilators includes a portion having a constant diameter.
 12. Thesystem of claim 10, wherein the first and second elongate dilators areseparate components, the second elongate dilator including a lumen forreceiving at least part of the first elongate dilator.
 13. The system ofclaim 11, further comprising a taper between the constant diameterportions of the first and second elongate dilators.
 14. The system ofclaim 12, further comprising a locking mechanism on at least one of thefirst or second dilators configured to prevent relative movementtherebetween.
 15. The system of claim 10, wherein a largest portion ofeach of the plug and of the second elongate dilator have substantiallyequal diameters.
 16. The system of claim 1, wherein the first and secondconnecting structures are configured to magnetically couple.
 17. Asystem for facilitating fluid connection between a blood pump and acirculatory system of a patient, comprising: a cannula having proximaland distal ends, the distal end of the cannula adapted to be in fluidcommunication with the circulatory system, the proximal end of thecannula configured to couple to an inlet of the blood pump; a plugconfigured to be inserted into the proximal end of the cannula; and atunneling device configured to be inserted into a body of a patient;wherein the plug further comprises a first connecting structure; andwherein the tunneling device further comprises a second connectingstructure, wherein the first and second connecting structures areselectively engageable to allow in situ connection and disconnectionbetween the cannula and tunneling device.
 18. A method of facilitatingfluid connection between a blood pump and a circulatory system of apatient, comprising: directing a distal end of a cannula into fluidcommunication with the circulatory system; inserting the blood pump intoa body of the patient; inserting a tunneling device into the body of thepatient; selectively engaging a first connecting structure of thecannula with a second connecting structure of the tunneling device;directing a proximal end of the cannula adjacent to an inlet of theblood pump; and connecting the proximal end of the cannula to the inlet.19. The method of claim 18, wherein directing the proximal end of thecannula step further comprises: retracting at least a portion of thetunneling device such that a distal end thereof moves towards the pump.20. The method of claim 18, wherein the tunneling device furthercomprises a first elongate dilator, and a second elongate dilatorproximal of the first elongate dilator, wherein at least a portion ofthe second elongate dilator has a larger diameter than that of the firstelongate dilator, and directing the tunneling device step furthercomprises: dilating an intercostal space by a first amount with thefirst elongate dilator; and dilating the intercostal space by a secondamount with the second elongate dilator.
 21. The method of claim 19,wherein the first and second elongate dilators are separate componentsand retracting step further comprises moving the first elongate dilatorproximally relative to the second elongate dilator.
 22. The method ofclaim 19, wherein the retracting step further comprises dilating anintercostal space with a cannula plug inserted into the proximal end ofthe cannula.
 23. The system of claim 1, wherein the second connectingstructure is defined at least in part by threads and the firstconnecting structure is defined at least in part by threads for matingwith the threads of the second connecting structure, and wherein thetunneling device further includes a detachable tip having threads formating with the threads of the second connecting structure.
 24. Thesystem of claim 23, wherein the tunneling device further includes anelongate member coupled with the second connecting structure forproviding selective rotation of the threads of the second connectingstructure.
 25. The system of claim 23, wherein the first connectingstructure further includes an independently rotatable sleeve defined atleast in part by the threads of the first connecting structure formating with the threads of the second connecting structure.
 26. Thesystem of claim 2, wherein: the second connecting structure is definedat least in part by threads; the tunneling device further includes adetachable tip having threads for mating with the threads of the secondconnecting structure; and the first connecting structure furtherincludes: an anchor positioned substantially within the plug; a pegaffixed to the anchor such that at least a portion of the peg protrudesfrom an end of the plug; and a sleeve defined at least in part bythreads for mating with the threads of the second connecting structure,the sleeve being positioned over the peg and attached thereto such thatthe sleeve may be rotated independent of the plug.
 27. The system ofclaim 5, wherein the second connecting structure is defined at least inpart by a clip comprising a sleeve having a plurality of expandableflanges and the first connecting structure is defined at least in partby a pin for frictionally engaging the clip of the second connectingstructure, and wherein the tunneling device further includes adetachable tip having a pin for frictionally engaging the clip of thesecond connecting structure.
 28. The system of claim 27, wherein atleast one of the pin of the first connecting structure and the pin ofthe detachable tip has a relief channel, and wherein the clip furtherincludes at least one tooth positioned on at least one of the pluralityof flanges such that the at least one tooth is engageable with therelief channel for securing the pin relative to the clip.
 29. The systemof claim 27, wherein at least one of the pin of the first connectingstructure and the pin of the detachable tip is tapered to provide smoothexpansion of the flanges.
 30. The system of claim 27, wherein the secondconnecting structure further comprises a retention sleeve for securingthe plurality of flanges over at least one of the pin of the firstconnecting structure and the pin of the detachable tip.
 31. The systemof claim 30, wherein at least one of the clip and the retention sleevecomprises a taper.
 32. The system of claim 2, wherein: the secondconnecting structure is defined at least in part by a clip comprising asleeve having a plurality of expandable flanges; the tunneling devicefurther includes a detachable tip having a pin for frictionally engagingthe clip of the second connecting structure; and the first connectingstructure further includes an anchor positioned substantially within theplug and a pin affixed to the anchor, such that the pin may frictionallyengage the clip of the second connecting structure.
 33. The system ofclaim 7, wherein the tunneling device further includes a removable tip,and wherein the groove of the second connecting structure is positionedon the removable tip.
 34. The method of claim 18, wherein selectivelyengaging the connecting structures further includes removing adetachable tip of the tunneling device.
 35. The method of claim 34,wherein the second connecting structure includes threads and wherein thefirst connecting structure and the detachable tip include threads formating with the threads of the second connecting structure, andselectively engaging the connecting structures further includes:disengaging the threads of the detachable tip from the threads of thesecond connecting structure; and engaging the threads of the firstconnecting structure with the threads of the second connectingstructure.
 36. The method of claim 35, wherein the first connectingstructure further includes an independently rotatable sleeve defined atleast in part by the threads of the first connecting structure formating with the threads of the second connecting structure, and engagingthe threads of the first connecting structure with the threads of thesecond connecting structure includes rotating the sleeve independent ofthe cannula plug.
 37. The method of claim 34, wherein the secondconnecting structure includes a clip comprising a sleeve having aplurality of expandable flanges and wherein the first connectingstructure and the detachable tip each include a pin for frictionallyengaging the clip, and selectively engaging the connecting structuresfurther includes: disengaging the pin of the detachable tip from theclip of the second connecting structure; and engaging the pin of thefirst connecting structure with the clip of the second connectingstructure.
 38. The method of claim 37, wherein engaging the pin of thefirst connecting structure with the clip of the second connectingstructure includes allowing the plurality of flanges to expand aroundthe pin such that the plurality of flanges may frictionally engage thepin.
 39. The method of claim 37, wherein the pin of the first connectingstructure has a relief channel, and wherein the clip further includes atleast one tooth positioned on at least one of the plurality of flangessuch that the at least one tooth is engageable with the relief channelfor securing the pin relative to the clip, and engaging the pin of thefirst connecting structure with the clip includes allowing the at leastone tooth to engage with the relief channel.
 40. The method of claim 37,wherein selectively engaging the connecting structures further comprisespositioning a retention sleeve over the clip for securing the pluralityof flanges over the pin of the first connecting structure.
 41. Themethod of claim 18, wherein: the second connecting structure includes agroove on the tunneling device; the first connecting structure includesa cavity for receiving a distal portion of the tunneling device and arib engageable with the groove for securing the tunneling devicerelative to the cannula; and selectively engaging the connectingstructures includes inserting the distal portion of the tunneling deviceinto the cavity of the first connecting structure and allowing the ribof the first connecting structure to engage with the groove of thesecond connecting structure.
 42. The method of claim 18, furthercomprising disengaging the connecting structures.